Yaw-rate sensor

ABSTRACT

A yaw-rate sensor having a substrate and a plurality of movable substructures that are mounted over a surface of the substrate, the movable substructures being coupled to a shared, in particular, central spring element, means being provided for exciting the movable substructures into a coupled oscillation in a plane that extends parallel to the surface of the substrate, the movable substructures having Coriolis elements, means being provided for detecting deflections of the Coriolis elements induced by a Coriolis force, a first Coriolis element being provided for detecting a yaw rate about a first axis, a second Coriolis element being provided for detecting a yaw rate about a second axis, the second axis being oriented perpendicularly to the first axis.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a yaw-rate sensor.

2. Description of Related Art

Linearly oscillating yaw-rate sensors are generally known. In theseyaw-rate sensors, parts of the sensor structure are actively set intooscillation (primary oscillation) in one direction, i.e., along a firstaxis (x-axis) that is oriented parallel to a substrate surface. Inresponse to an external yaw rate about one particular sensitive axis,Coriolis forces act on the oscillating parts of the sensor structure.These Coriolis forces, which vary periodically with the frequency of theprimary oscillation, induce oscillations in parts of the sensorstructure (secondary oscillation) in the direction of a second axis thatis oriented perpendicularly to the x-axis. The second axis can beoriented parallel to the substrate surface or perpendicularly to thesubstrate surface. Detection means, which capacitively sense thesecondary oscillation via electrodes, are mounted on the sensorstructure.

To an increasing degree, applications demand yaw-rate sensors that arecapable of detecting yaw rates about a plurality of mutuallyperpendicularly extending axes. Till now, this has been accomplished byplacing a plurality of monoaxial sensors laterally or verticallyside-by-side. However, in terms of costs, space requirements, powerrequirements, and the relative orientation accuracy of the axes, thereare disadvantages entailed in using a plurality of monoaxial yaw-ratesensors.

Furthermore, biaxial yaw-rate sensors are known from the related artwhich are capable of detecting yaw rates about two mutuallyperpendicularly extending axes that are oriented parallel to thesubstrate surface.

SUMMARY OF THE INVENTION

An object of the present invention is to devise an improved biaxialyaw-rate sensor that is capable of sensing yaw rates about two mutuallyperpendicularly extending spatial axes. It is also an object of thepresent invention to devise a triaxial yaw-rate sensor that is capableof sensing yaw rates about all three spatial axes.

The present invention provides that the yaw-rate sensor have a pluralityof movable substructures that are mounted over a surface of thesubstrate. The substructures are coupled via a shared, in particular,central spring element and may be excited into a coupled oscillation ina plane that extends parallel to the surface of the substrate. Each ofthe substructures has one or more Coriolis elements that are providedfor detecting deflections induced by a Coriolis force.

Because the substructures are mechanically coupled, the yaw-rate sensoradvantageously has a defined, shared drive mode and, therefore, requiresonly one drive control circuit. This reduces the space and powerrequirements for the electronic evaluation circuit.

In one preferred specific embodiment, two substructures of the yaw-ratesensor are excited into a drive mode which induces an antiparallel,antiphase deflection of the two movable substructures along a sharedaxis.

The center of mass of this type of yaw-rate sensor advantageouslyremains fixed during one period of the primary oscillation. Neither alinear pulse nor an angular momentum is outcoupled by the yaw-ratesensor, thereby minimizing the energy exchange with the surroundings.

In another preferred specific embodiment, the yaw-rate sensor has fourmovable substructures that are coupled to one another via a centralspring element and are excitable into a coupled oscillation mode in aplane that extends parallel to the substrate surface. In this context,the first and the second movable substructures execute an antiparalleloscillation in the direction of a first axis, while the third and thefourth movable substructures execute an antiparallel oscillation in thedirection of a second axis that is oriented perpendicularly to the firstaxis.

The coupled oscillation mode of the yaw-rate sensor composed of foursubstructures is likewise advantageously excitable by a shared drivecontrol circuit, whereby the space and power requirements of theelectronic evaluation circuit are reduced.

In addition, the yaw-rate sensor composed of four substructures also hasthe advantage of a fixed center of mass for the duration of oneoscillatory period. As a result, neither a linear pulse nor an angularmomentum is outcoupled by the yaw-rate sensor.

A further advantage of the yaw-rate sensor composed of foursubstructures is the feasibility of integrating Coriolis elements fordetecting yaw rates about all three spatial axes. Since the Coriolisforce exerted on a Coriolis element acts perpendicularly to the drivedirection of the Coriolis element and perpendicularly to the rotary axisof motion of a yaw rate, a yaw rate about a rotary axis of motionextending parallel to the drive direction of the Coriolis element doesnot produce a Coriolis force. Since the primary oscillation of theinventive yaw-rate sensor, which is composed of four movablesubstructures, has motion components in more than only one spatialdirection, yaw rates may be detected about any given spatial axis.

In a further refinement of the preferred specific embodiment, at leasttwo substructures that oscillate in phase opposition have identicalCoriolis elements for detecting a yaw rate about the same axis. Theopposite-phase primary oscillation of the substructures bearing theidentical Coriolis elements advantageously induces an opposite-phasesecondary oscillation of the Coriolis elements. This renders possible afully differential analysis of the detection signal. In addition, theantiparallel drive and detection motion reduces the yaw-rate sensor'ssusceptibility to interference caused by occurring linear accelerations.

In another preferred specific embodiment, the Coriolis elements of ayaw-rate sensor are not only coupled in terms of a drive motion, butalso in a detection mode. This advantageously prevents an unintentionalsplitting of the detection frequencies of the various Coriolis elementsof the yaw-rate sensor.

The biaxial and triaxial yaw-rate sensors provided by the presentinvention may be advantageously manufactured cost-effectively and bymass production using standard surface micromachining processes.

The present invention is described in greater detail in the followingwith reference to the figures. Like reference numerals denote identicalor corresponding parts.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a biaxial yaw-rate sensor for detecting yaw rates about they- and z-axis.

FIG. 2 shows a biaxial yaw-rate sensor for detecting yaw rates about they- and z-axis.

FIG. 3 shows a known micromechanical flexural spring.

FIG. 4 shows a flexural spring designed as a ladder spring.

FIG. 5 shows a biaxial yaw-rate sensor for detecting yaw rates about they- and z-axis.

FIG. 6 shows a biaxial yaw-rate sensor for detecting yaw rates about thex- and y-axis.

FIG. 7 shows a schematic representation of a drive mode of a yaw-ratesensor composed of four substructures.

FIG. 8 shows a schematic representation of a drive mode of a yaw-ratesensor composed of four substructures.

FIG. 9 shows a schematic representation of a biaxial yaw-rate sensor fordetecting yaw rates about the x- and y-axis.

FIG. 10 shows a schematic representation of a triaxial yaw-rate sensorfor detecting yaw rates about all three spatial axes.

FIG. 11 shows a schematic representation of a triaxial yaw-rate sensorfor detecting yaw rates about all three spatial axes.

FIG. 12 shows a schematic representation of a triaxial yaw-rate sensorhaving reduced space requirements.

FIG. 13 shows a schematic representation of a triaxial yaw-rate sensor.

FIG. 14 shows a schematic representation of a triaxial yaw-rate sensor.

FIG. 15 shows a schematic representation of a triaxial yaw-rate sensor.

FIG. 16 shows a schematic representation of a triaxial yaw-rate sensor.

FIG. 17 shows a schematic representation of a triaxial yaw-rate sensorcomposed of six substructures.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a view of a biaxial yaw-rate sensor 100. Yaw-rate sensor100 includes two movable substructures 51 which are mounted over asubstrate 50 that extends in the plane of the paper. The edge length ofyaw-rate sensor 100 is a few hundred micrometers.

Movable substructures 51 are manufactured out of a material that, at thevery bottom, has a thick silicon substrate upon which there is an oxidelayer. Above the oxide layer, there is a polysilicon layer VP that formsa circuit trace plane. This is followed by another oxide layer OX, uponwhich a silicon layer EP is deposited, out of which the movablecomponents of the yaw-rate sensors are manufactured. Recesses areprovided at special sites in oxide layer OX. Connections between siliconlayer EP and circuit trace plane VP are formed in these recesses duringdeposition of silicon layer EP. The sensor elements are then defined,and oxide layer OX is removed in an etching process. Self-supportingstructures are thereby produced.

Each of movable substructures 51 has a drive frame 52. Drive frames 52may have perforations, which are not shown in FIG. 1 for the sake ofclarity. Each drive frame 52 is connected via four connecting flexuralsprings 53 to substrate 50.

Connecting flexural springs 53 are designed as bar springs that arefolded in a meander shape and are oriented in such a way that movablesubstructure 51 is movable in the x-direction extending in the plane ofthe paper, but, on the other hand, is fixed in all other spatialdirections. Connecting flexural springs 53 may also have a differentgeometry which ensures a directionally dependent spring stiffness.

Drive frame 52 of each movable substructure 51 may be set intooscillation in the x-direction via two drive comb structures 56. Eachdrive comb structure 56 is composed of a part that is connected tosubstrate 50 and of a part that is connected to drive frame 52. Bothparts of drive comb structure 56 have comb structures whose tinesintermesh without contacting each other. Through the application ofhomopolar or oppositely poled voltage to both parts of a drive combstructure 56, a force in the x-direction may be exerted on a movablesubstructure 51, and movable substructure 51 may be set intooscillation. The oscillation of movable substructure 51 may be detectedvia two further capacitive, drive-detection comb structures 57 affixedto drive frame 42. The design of drive-detection comb structures 57corresponds to that of drive comb structures 56. The two drive-detectioncomb structures 57 are preferably attached at opposite sides of movablesubstructure 51 to permit a differential detection of the driveoscillation.

At the outer edge facing the respective other drive frame 52, each driveframe 52 has a connecting piece 102. The two connecting pieces 102 areconnected to a central connection spring 101. The two movablesubstructures 51 are thereby coupled via central connection spring 101.Central connection spring 101 is composed of two bars of substratematerial that are folded in a meander shape. Central connection spring101 may also have a different geometry.

The two movable substructures 51 have two Coriolis elements 58 each.Coriolis elements 58 have a substantially rectangular form. A firstCoriolis element 58 of each movable substructure 51 is a grid-structureCoriolis element 70. A second Coriolis element 58 of each movablesubstructure 51 is a rocker-type Coriolis element 80. Coriolis elements58 are mounted on movable substructures 51 in such a way that yaw-ratesensor 100 is mirror-symmetrical to a plane that is orientedperpendicularly to the surface of substrate 50, between movablesubstructures 51.

Grid-structure Coriolis element 70 has a frame 71. At two sides of frame71 opposing one another in the y-direction, frame 71 is connected ineach case via two flexural springs 72 to drive frame 52. The fourflexural springs 72 that are folded in a meander shape are primarilyextensible in the y-direction due to the orientation of their folds,while an oscillation of drive frame 52 in the x-direction is completelytransmitted to frame 71 of grid-structure Coriolis element 70. Theregion of grid-structure Coriolis element 70 enclosed by frame 71 hasmovable electrodes 73. Fixed electrodes 74, which are connected to thesubjacent circuit trace plane, are located in the empty spaces of thegrid structure. Electrodes 73, 74 permit detection of a deflection ofgrid-structure Coriolis element 70 in the y-direction.

Rocker-structure Coriolis element 80 has a rocker element 81. Rockerelement 81 is composed of two elements having a different mass that areconfigured side-by-side in the y-direction and are joined by acrosspiece. The crosspiece is connected on both sides to drive frame 52via two torsion springs 82 that are oriented parallel to the x-axis.Moreover, there is no connection between rocker element 81 and driveframe 52. Torsion springs 82 allow rocker element 81 to rotate about anaxis formed by torsion springs 82. Apart from the rotation about thisaxis that extends parallel to the x-axis, rocker-structure Corioliselement 80 ideally does not have any further degrees of freedom ofmovement relative to drive frame 52. An oscillation of movablesubstructure 51 in the x-direction is completely transmitted torocker-structure Coriolis element 80. A detection electrode 83 isprovided on substrate 50 underneath each of the two parts of rockerelement 81. A rotation of rocker element 81 effects a change in thecapacitance between detection electrodes 83 and rocker element 81,allowing it to be thereby differentially detected.

The drive frequency of drive comb structures 56 is preferably selectedin a way that allows the two movable substructures 51 to be excited intoan antiparallel oscillation in the x-direction, accompanied by antiphasedeflection of the two movable substructures 51. Since the two movablesubstructures 51 are mutually symmetrical in form and essentially havethe same mass, the center of mass of yaw-rate sensor 100 during oneperiod of the antiparallel primary oscillation remains fixed. Thus,neither a linear pulse nor an angular momentum is outcoupled by yaw-ratesensor 100, thereby minimizing the energy exchange with thesurroundings.

In response to the occurrence of a yaw rate about the z-axis, a Coriolisforce acts in the y-direction on grid-structure Coriolis elements 70 ofthe first and second movable substructure 51. This Coriolis forceinduces a deflection of grid-structure Coriolis elements 70 in they-direction which may be detected via movable electrodes 73 andelectrodes 74 connected to substrate 50. Due to the opposite-phaseoscillation of the two movable substructures 51, the Coriolis force actsin opposite directions on both grid-structure Coriolis elements 70.During the first half of an oscillatory period of movable substructures51, a Coriolis force acts in the positive y-direction on firstgrid-structure Coriolis element 70, for example, while a Coriolis forceacts in the negative y-direction on second grid-structure Corioliselement 70. During the next half of the oscillatory period, a Coriolisforce acts in the negative y-direction on first grid-structure Corioliselement 70, while a Coriolis force acts in the positive y-direction onsecond grid-structure Coriolis element 70. Thus, a differential analysisof the deflections of grid-structure Coriolis elements 70 detected byelectrodes 73, 74 is made possible. In this manner, any interference inyaw-rate detection due to linear accelerations possibly actingadditionally on yaw-rate sensor 100 is suppressed.

In response to the occurrence of a yaw rate about the z-axis, a Coriolisforce likewise acts in the y-direction on first and second movablesubstructure 51. However, a deflection of movable substructures 51 inthe y-direction is suppressed forcefully enough due to connectingflexural springs 53 that feature y-direction stiffness. A Coriolis forcealso acts in the y-direction on rocker-structure Coriolis elements 80.However, a deflection of rocker-structure Coriolis elements 80 in they-direction is likewise not possible, respectively is suppressed veryforcefully, due to torsion springs 82 that feature y-directionstiffness. Moreover, a deflection in parallel to the substrate surfacedoes not lead to any changes in capacitance at electrodes 83 connectedto the substrate.

In response to the occurrence of a yaw rate about the y-axis, a Coriolisforce acts in the z-direction on grid-structure Coriolis elements 80 ofthe first and second movable substructure 51. Due to the asymmetricaldistribution of the mass of rocker element 81 of rocker-structureCoriolis elements 80 over the two sides of torsion springs 82, theCoriolis force acting in the z-direction induces a rotation of rockerelements 81 about the axis of torsion springs 82 that is orientedparallel to the x-axis. The rotation of rocker elements 81 may bedetected as a function of changes in capacitance at detection electrodes83. Due to the antiparallel oscillatory motion of the two movablesubstructures 51, the Coriolis force acts in opposite directions on bothrocker-structure Coriolis elements and induces a rotation of the tworocker-structure Coriolis elements 80 in opposite directions ofrotation. In this manner, the changes in the capacitance of detectionelectrodes 83 may be analyzed differentially, and any interference inyaw-rate detection due to linear accelerations possibly actingadditionally on yaw-rate sensor 100 is suppressed.

In response to the occurrence of a yaw rate about the y-axis, a Coriolisforce likewise acts in the z-direction on drive frame 52 of first andsecond movable substructure 51. However, a deflection of drive frame 52in the z-direction is not possible due to connecting flexural springs 53that feature z-direction stiffness. A Coriolis force also acts in thez-direction on rocker-structure Coriolis elements 70. However, az-direction deflection of grid-structure Coriolis elements 70 islikewise not possible due to flexural springs 72 that featurez-direction stiffness.

FIG. 2 shows a schematic representation of a biaxial yaw-rate sensor200. Yaw-rate sensor 200 differs from yaw-rate sensor 100 illustrated inFIG. 1 in that rocker-structure Coriolis element 80 is replaced by atrampoline-structure Coriolis element 90 in each of the two movablesubstructures 51.

Each of the two trampoline-structure Coriolis elements 90 has asubstantially rectangular seismic mass 91. Seismic mass 91 is connectedvia four flexural springs 92 to drive frame 52 and is otherwise freelymovable. Each flexural spring 92 engages approximately in the middle ofa side edge of seismic mass 91, extends parallel to the side edge ofseismic mass 91 within a gap between seismic mass 91 and drive frame 52to approximately the middle of an adjacent side edge of seismic mass 91,and is connected there to drive frame 52. Flexural springs 92advantageously feature x- and y-direction stiffness, so that seismicmass 91 is not able to be deflected toward drive frame 52 in the x- andy-directions. In the z-direction, flexural springs 92 permit a uniform,coplanar deflection of seismic mass 91 toward drive frame 52. Adetection electrode 94 is provided on substrate 50 underneath seismicmass 91. A deflection of seismic mass 91 induces a change in capacitanceat detection electrode 94, thereby permitting detection of the same.

In response to the occurrence of a yaw rate about the y-axis, a Coriolisforce acts in the z-direction on the two trampoline-structure Corioliselements 90 and induces a z-direction deflection of seismic masses 91.Due to the antiphase movement of the two movable substructures 51, theCoriolis force acts on the two trampoline-structure Coriolis elements 90in opposite directions and induces an opposite deflection of the twoseismic masses 91. Therefore, the deflection of the two seismic masses91 may take place differentially by detection electrodes 94. As aresult, yaw-rate sensor 200 is insensitive to interference caused bylinear accelerations in the z-direction.

FIG. 3 shows a schematic representation of a known kinked flexuralspring 92 that may be used for suspending seismic mass 91 of atrampoline-structure Coriolis element 90. Flexural spring 92 is made ofa single, long, narrow bar of silicon. In a middle region, the bar has a90° kink. Provided at both ends of the bar at a 90° angle thereto areendpieces, via which flexural spring 92 may be connected to othermicromechanical components, for example, to a seismic mass 91 and to adrive frame 52 of a trampoline-structure Coriolis element 90.

FIG. 4 shows a schematic representation of a ladder spring 93 that maylikewise be used for suspending a seismic mass 91 in atrampoline-structure Coriolis element 90. Ladder spring 93 is composedof two parallel, long, narrow bars of silicon, which are joined multipletimes over the length thereof by rungs 95 of silicon. The interspacingbetween two rungs 95 is greater than the distance between the twoparallel bars of ladder spring 93. In a middle region, ladder spring hasa 90° kink. Provided at both ends of ladder spring 93 at a 90° anglethereto are endpieces, via which ladder spring 93 may be connected toother micromechanical components, for example, to a seismic mass 81 andto a drive frame 52 of a trampoline-structure Coriolis element 90. Incomparison to flexural spring 92 from FIG. 3, ladder spring 93 has asubstantially greater ratio of stiffness in the x- and y-direction tothe stiffness in the z-direction. This makes ladder spring 93 bettersuited for suspending seismic mass 91 of a trampoline-structure Corioliselement than flexural spring 92. Ladder spring 93 may also be used forany other given micromechanical components which require a springelement featuring anisotropic stiffness of the spring.

FIG. 5 shows a schematic representation of another biaxial yaw-ratesensor 500 for detecting yaw rates about the y- and z-axis. Yaw-ratesensor 500 includes four movable substructures 51. The four movablesubstructures 51 are coupled via connecting pieces 102 to a centralconnection spring 501. Connection spring 501 is composed of a bar ofsubstrate material that is folded in a meander shape. Connection spring501 may also have a different design.

A first and a second movable substructure 51 are configured to permitexcitation thereof into a coupled oscillation in the x-direction. Athird and a fourth movable substructure 51 are configured to permitexcitation thereof into a coupled oscillation in the y-direction.Central connection spring 501 couples the oscillation of first andsecond substructure 51 and the oscillation of third and fourth movablesubstructure 51 to one another. The four movable substructures 51 ofyaw-rate sensor 500 may be excited into a common drive mode that inducesa superimposed deflection of the four movable substructures 51 in the x-and y-direction. Two possible drive modes are schematically illustratedin FIGS. 7 and 8. The drive mode (breathing mode) 700 shown in FIG. 7induces a simultaneous movement of all four movable substructures 51toward central connection spring 501 or away therefrom. In drive mode(anti-breathing mode) 701 shown in FIG. 8, the two substructures 51 thatare movable in the x-direction move in a first half of an oscillatoryperiod toward central connection spring 501, while the two substructures51 that are movable in the y-direction move away from central connectionspring 501. In a second half of an oscillatory period, the twosubstructures 51 that are movable in the x-direction move away fromcentral connection spring 501, while substructures 51 that are movablein the y-direction move toward central connection spring 501. Centralconnection spring 501 induces a frequency splitting of the two drivemodes 700, 701 of yaw-rate sensor 500 illustrated in FIGS. 7 and 8. Oneof the two drive modes 700, 701 is selectively excitable in response toa defined introduction of force, in-phase, in the x- and y-direction bydrive comb structures 56 provided on movable substructures 51 ofyaw-rate sensor 500.

Unlike yaw-rate sensors 100, 200 illustrated in FIGS. 1 and 2, each ofmovable substructures 51 of yaw-rate sensor 500 illustrated in FIG. 5features merely one Coriolis element 58. First and second substructures51 that are movable in the x-direction each have a trampoline-structureCoriolis element 90. Third and fourth substructures 51 that are movablein the y-direction each have a grid-structure Coriolis element 70.

In response to the occurrence of a yaw rate about the y-axis, a Coriolisforce acts in the z-direction on first and second substructures 51 thatare movable in the x-direction and induces a deflection of seismicmasses 91 of trampoline-structure Coriolis elements 90 in the directionof the z-axis. The antiparallel movement of first and second movablesubstructures 51 induces a deflection of seismic masses 91 in oppositedirections and permits a differential analysis by detection electrodes94 of trampoline-structure Coriolis elements 90.

In response to the occurrence of a yaw rate about the z-axis, a Coriolisforce acts in the x-direction on third and fourth substructures 51 thatare movable in the y-direction and induces a deflection of frames 71 ofgrid-structure Coriolis elements 70 along the x-axis. Due to theantiparallel movement of third and fourth movable substructures 51,frames 71 of both grid-structure Coriolis elements 70 are deflected inopposite directions, thereby permitting a differential analysis.

FIG. 6 shows a schematic representation of a biaxial yaw-rate sensor fordetecting yaw rates about the x- and y-axis. Yaw-rate sensor 600 differsfrom yaw-rate sensor 500 illustrated in FIG. 5 in that substructures 51that are movable in the y-direction also have trampoline-structureCoriolis elements 90 instead of grid-structure Coriolis elements 70. Inresponse to the occurrence of a yaw rate about the x-axis, a Coriolisforce acts in the z-direction on substructures 51 that are movable inthe y-direction and induces a deflection of seismic mass 91 oftrampoline-structure Coriolis elements 90 in the direction of thez-axis. Due to the antiparallel movement of substructures 51 that aremovable in the y-direction, the Coriolis force induces an oppositedeflection of the two seismic masses 91 that may be differentiallyanalyzed.

FIG. 9 shows a schematic representation of a biaxial yaw-rate sensor 900for detecting yaw rates about the x- and y-axis. As does yaw-rate sensor600 illustrated in FIG. 6, yaw-rate sensor 900 features four movablesubstructures 51 which each include a trampoline-structure Corioliselement 90. However, in comparison to FIG. 6, drive frames 52 of movablesubstructures 51 are replaced by two-piece drive frames 902. There is noconnection between two-piece drive frames 902 and central connectionspring 501. Instead, central connection spring 501 is connected viaconnecting pieces 901 to seismic masses 91 of trampoline-structureCoriolis elements 90. In addition, seismic masses 91 oftrampoline-structure Coriolis elements 90 are connected to substrate 50via additional connecting elements 903 on the side of each movablestructure 51 facing away from central connection spring 501. The resultof the coupling of seismic masses 91 via central connection spring 51 isthat Coriolis elements 58 are not only coupled in terms of the drivemotion, but also in the detection mode. In this exemplary embodiment,flexural springs 904, which connect seismic masses 91 to drive frame902, have a U-shaped design.

Differences in the masses of two substructures 51 or in the springstiffness of flexural springs 92 or 904 of two Coriolis elements 58 thatare inherent in the process engineering may lead to an unwantedsplitting of the detection frequencies of both Coriolis elements 58,resulting in different phase relations between the drive motion and thedetection motion of Coriolis elements 58. A simple analysis of the twodetection channels, for example, via a shared evaluation path in themultiplexing operation, is thereby made difficult since the signals mustbe detected at different phases. An electronic quadrature compensationis also significantly impeded. It is possible to overcome this problemby coupling the detection modes of Coriolis elements 58 of the fourmovable substructures 51.

FIG. 10 shows a schematic representation of a triaxial yaw-rate sensor1000 for detecting yaw rates about the x-, y- and z-axis. As do yaw-ratesensors 500, 600 illustrated in FIGS. 5 and 6, triaxial yaw-rate sensor1000 is composed of four movable substructures 51 which are coupled viaconnecting pieces 102 to a central connection spring 501. In contrast toyaw-rate sensors 500, 600, each movable substructure 51 of yaw-ratesensor 1000 has two Coriolis elements 58. Each movable substructure 51includes a rocker-structure Coriolis element 80, as well as agrid-structure Coriolis element 70.

In response to the occurrence of a yaw rate about the y-axis, a Coriolisforce acts in the direction of the z-axis on substructures 51 that aremovable in the x-direction and induces a rotation of rocker elements 81of rocker-structure Coriolis elements 80 of substructures 51, which aremovable in the x-direction, about torsion springs 82 that are orientedparallel to the x-axis. The antiparallel movement of the twosubstructures 51 that are movable in the x-direction permits adifferential analysis of the tilting of rocker elements 81 induced bythe Coriolis force and thus a detection of a yaw rate about the y-axis.

In response to the occurrence of a yaw rate about the x-axis, a Coriolisforce in the z-direction acts on substructures 51 that are movable inthe y-direction and induces a rotation of rocker elements 81 ofrocker-structure Coriolis elements 80 of substructures 51, which aremovable in the y-direction, about torsion springs 82 that are orientedparallel to the y-axis. Due to the antiparallel movement of the twosubstructures 51 that are movable in the y-direction, a differentialanalysis of the rotation of rocker elements 81 is possible.

In response to the occurrence of a yaw rate about the z-axis, a Coriolisforce in the y-direction acts on substructures 51 that are movable inthe x-direction and induces a deflection of frames 71 of grid-structureCoriolis elements 70 of substructures 51, which are movable in thex-direction, in the direction of the y-axis. Due to the antiparallelmovement of the two substructures 51 that are movable in thex-direction, a differential analysis of the deflection of frames 71induced by the Coriolis force is possible.

In addition, in response to the occurrence of a yaw rate about thez-axis, a Coriolis force in the direction of the x-axis acts onsubstructures 51 that are movable in the y-direction and induces adeflection of frames 71 of grid-structure Coriolis elements 70 ofsubstructures 51, which are movable in the y-direction, in the directionof the x-axis. Due to the antiparallel movement of the two substructures51 that are movable in the y-direction, this deflection may also bedifferentially detected. Overall, therefore, four Coriolis elements 58are available to determine a yaw rate about the z-axis.

FIG. 11 shows a schematic representation of another triaxial yaw-ratesensor 1100 for determining yaw rates about all three spatial axes. Incomparison to yaw-rate sensor 1000 illustrated in FIG. 10, the fourrocker-structure Coriolis elements 80 for determining yaw rates aboutthe x- and y-axis are replaced by trampoline-structure Coriolis elements90. These are likewise suited for differentially detecting yaw ratesabout the x- and y-axis.

Triaxial yaw-rate sensors 1000, 1100 from FIG. 10, 11 feature moreCoriolis elements 58 than needed for determining yaw rates about thez-axis. FIG. 12 shows a schematic representation of a triaxial yaw-ratesensor 1200 which, in design, resembles yaw-rate sensor 1000 in FIG. 10.Absent, however, in substructures 51 that are movable in the y-directionare grid-structure Coriolis elements 70. Thus, substructures 51 that aremovable in the y-direction each include only one rocker-structureCoriolis element 80. Merely grid-structure Coriolis elements 70 ofsubstructures 51 that are movable in the x-direction are used fordetecting yaw rates about the z-axis. In addition, connecting pieces 102between drive frames 52 of substructures 51 that are movable in they-direction, and central connection spring 501 are significantlyshortened compared to connecting pieces 102 between drive frames 52 ofmovable structures 51 that are movable in the x-direction, and centralconnection spring 501, so that substructures 51 that are movable in they-direction are configured in the region of the surface of substrate 50that is disposed between the substructures that are movable in thex-direction. This reduces the space requirements for yaw-rate sensor1200.

Substructures 51 of yaw-rate sensor 1200 that are movable in they-direction feature merely one Coriolis element 58 each, whilesubstructures 51 of yaw-rate sensor 1200 that are movable in thex-direction include two Coriolis elements 58 each. As a result,substructures 51 that are movable in the y-direction have a smaller massthan substructures 51 that are movable in the x-direction. In onepreferred specific embodiment, this mass differential is compensated bydifferent spring stiffness levels of central connection springs 501 inthe x- and y-direction. In this specific embodiment, central connectionspring 501 has a lower spring stiffness in the y-direction than in thex-direction. The spring stiffness levels are selected to allowsubstructures 51 that are movable in the y-direction to execute anoscillation having a deflection amplitude comparable to that ofsubstructures 51 that are movable in the x-direction. The stiffness ofcentral connection spring 501 may be adjusted by varying the length andthickness of the individual spring members.

FIG. 13 shows a schematic representation of another triaxial yaw-ratesensor 1300 for detecting yaw rates about all three spatial axes.Yaw-rate sensor 1300 includes four movable substructures 51.Substructures 51 that are movable in the x-direction each feature twoCoriolis elements 58 for detecting yaw rates about the y- and z-axis.Substructures 51 that are movable in the y-direction feature oneCoriolis element 58 each for differentially detecting yaw rates aboutthe x-axis.

Substructures 51 that are movable in the x-direction each have atwo-piece grid-structure Coriolis element 1301 and a rocker-structureCoriolis element 80. The two-piece grid-structure Coriolis elements 1301have a U-shape and surround rocker-structure Coriolis elements 80without contacting the same. Due to this shape of two-piecegrid-structure Coriolis element 1301, substructures 51 that are movablein the x-direction feature a symmetry with respect to a mirror planethat extends parallel to the x-axis. Rocker-structure Coriolis elements80 of the two substructures 51 that are movable in the x-direction areused for differentially detecting yaw rates about the y-axis. The twotwo-piece grid-structure Coriolis elements 1301 of the two substructures51 that are movable in the x-direction are used for differentiallydetecting yaw rates about the z-axis.

The two substructures 51 that are movable in the y-direction each have arocker-structure Coriolis element 80. Compared to rocker-structureCoriolis elements 80 of substructures 51, that are movable in they-direction, of yaw-rate sensor 1200 illustrated in FIG. 12,rocker-structure Coriolis elements 80 of substructures 51, that aremovable in the y-direction, are rotated by 90°. As a result,substructures 51 that are movable in the y-direction feature both aninner symmetry with respect to a mirror plane that is parallel to they-axis, as well as a symmetry to one another. The principle of operationof trampoline-structure Coriolis elements 90 is not altered by theconfiguration that is rotated by 90°.

At the side edges extending parallel to the y-axis, drive frames 52 ofsubstructures 51 that are movable in the y-direction each feature acantilever 1302. Drive comb structures 56 for driving substructures 51that are movable in the y-direction, as well as capacitivedrive-detection comb structures 57 for detecting the drive motion ofsubstructures 51 that are movable in the y-direction are mounted oncantilevers 1302 of drive frames 52 of substructures 51 that are movablein the y-direction. Four connecting flexural springs 53 take up theentire side edges, extending parallel to the x-axis, of drive frames 52of substructures 51 that are movable in the y-direction. Thisconfiguration of drive comb structures 56, of capacitive drive-detectioncomb structures 57, as well as of connecting flexural springs 53 allowssmaller spatial dimensions of substructures 51 that are movable in they-direction and thus reduces the surface-area requirement of triaxialyaw-rate sensor 1300.

FIG. 14 shows another triaxial yaw-rate sensor 1400 for detecting yawrates about all three spatial directions. Yaw-rate sensor 1400corresponds to yaw-rate sensor 1200 shown in FIG. 12; in all fourmovable substructures 51, rocker-structure Coriolis element 80 havingbeen replaced by a trampoline-structure Coriolis element 90.Trampoline-structure Coriolis elements 90 of substructures 51 that aremovable in the y-direction permit a differential detection of yaw ratesabout the x-axis. Trampoline-structure Coriolis elements 90 ofsubstructures 51 that are movable in the x-direction permit adifferential detection of a yaw rate about the y-axis. Yaw-rate sensor1400 features a greater symmetry than yaw-rate sensor 1200.

FIG. 15 shows another specific embodiment of a triaxial yaw-rate sensor1500 for detecting yaw rates about the x-, y- and z-axis. Yaw-ratesensor 1500 includes four movable substructures 51. A central connectionspring 1501, which is designed as a circular thin ring of substratematerial, is located between movable substructures 51. Centralconnection spring 1501 is connected via four connecting pieces 1505 thatare perpendicularly attached in each instance at a 90° interval to driveframes 1502 of the four movable substructures 51. Central connectionspring 1501 may also have an elliptical shape to allow different springstiffness levels in the x- and y-direction.

Each movable substructure 51 is connected via four connecting flexuralsprings 1503 to substrate 50. Connecting flexural springs 1503 of eachmovable substructure 51 are oriented in such a way that, in thedirection of a first axis extending parallel to the surface of thesubstrate, movable substructure 51 is movably fastened in the directionof two axes extending perpendicularly thereto. A first and a secondmovable substructure 51 may be excited into an antiparallel oscillationin the x-axis direction. A third and a fourth movable substructure 51may be excited into an antiparallel oscillation in the y-axis direction.To excite an oscillation, each of movable substructures 51 features adrive comb structure 1504 which is located at the side of drive frame1502 facing away from central connection spring 1501 and takes up theentire side of drive frame 1502. In another specific embodiment, drivecomb structure 1504 only takes up a portion of the side of drive frame1502 and is supplemented by a drive-detection comb structure 57.

The four movable substructures 51 of yaw-rate sensor 1500 that areinterconnected by central connection spring 1501 may be excited into acoupled oscillation in the x- and y-direction that induces asuperimposed deflection of the four movable substructures 51 in the x-and y-direction. For example, drive modes 700, 701 schematicallyillustrated in FIGS. 7 and 8 may be excited.

Drive frames 1502 of the four movable substructures 51 feature a basichexagonal shape. Each drive frame 1502 is composed of a rectangularpart, to whose longitudinal side facing central connection spring 1501,the base of an equilateral trapezoid is joined. The rectangular part ofdrive frame 1502 of each movable substructure 51 has a grid-structureCoriolis element 70 for detecting a yaw rate about the z-axis. Thetrapezoidal part of drive frame 52 of each movable substructure 51 has atrampoline-structure Coriolis element 1510. Each trampoline-structureCoriolis element 1510 includes a trapezoidal seismic mass 1511 which isconnected in each case via four flexural springs 1512 to drive frame1502. Flexural springs 1512 are provided so as to allow seismic mass1511 to follow a movement of drive frame 1502 in the x- and y-direction,while seismic mass 1511 may be deflected in the z-direction toward driveframe 1502. If a yaw rate about the y-axis is present, a Coriolis forceacts in the direction of the z-axis on substructures 51 that are movablein the x-direction and induces a deflection of seismic masses 1511 oftrampoline-structure Coriolis elements 1510 of substructures 51 that aremovable in the x-direction along the z-axis. Due to the antiparallelmovement of substructures 51 that are movable in the x-direction,seismic masses 1511 of the two substructures 51 that are movable in thex-direction are deflected in opposite directions and permit adifferential detection of a yaw rate about the y-axis. The twotrampoline-structure Coriolis elements 1510 of substructures 51 that aremovable in the y-direction permit a differential determination of a yawrate about the x-axis.

FIG. 16 shows another triaxial yaw-rate sensor 1600 for determining yawrates about the x-, y- and z-axis. Yaw-rate sensor 1600 includes fourmovable substructures 51 which each feature a Coriolis element 58. Inthis context, one of substructures 51 that are movable in thex-direction has a rocker-structure Coriolis element 80; the othersubstructure 51 that is movable in the x-direction has a grid-structureCoriolis element 70. One of substructures 51 that are movable in they-direction has a grid-structure Coriolis element 70; the othersubstructure 51 that is movable in the y-direction has arocker-structure Coriolis element 80.

If the four movable substructures 51 of triaxial yaw-rate sensor 1600are excited into a common drive mode, then the two grid-structureCoriolis elements 70 permit a differential detection of a yaw rate aboutthe z-axis. Rocker-structure Coriolis element 80 of first substructure51 that is movable in the x-direction permits a detection of a yaw rateabout the y-axis. Rocker-structure Coriolis element 80 of secondsubstructure 51 that is movable in the y-direction permits a detectionof a yaw rate about the x-axis.

Since each of the four movable substructures 51 of triaxial yaw-ratesensor 1600 has only one Coriolis element 58, yaw-rate sensor 1600requires less surface area than yaw-rate sensor 1000 illustrated in FIG.10. However, antiparallel oscillating substructures 51 are not mutuallysymmetrical. It is possible to compensate for the different masses ofCoriolis elements 58 of the two antiparallel oscillating substructures51 by properly selecting the masses of drive frames 52 of the twoantiparallel oscillating substructures 51.

FIG. 17 shows a schematic representation of a triaxial yaw-rate sensor1700 which is composed of six movable substructures 51. Four movablesubstructures 51 of yaw-rate sensor 1700 form a biaxial yaw-rate sensorwhose design corresponds to that of yaw-rate sensor 600 illustrated inFIG. 6. For the sake of clarity, only some of connecting flexuralsprings 53 are shown, and neither drive comb structures 56 norcapacitive drive-detection comb structures 57 are included in theillustration. Two additional movable substructures 51, which are rotatedby 45° relative to first four movable substructures 51, are configuredon two sides of central connection spring 501 and are likewise connectedvia connecting pieces 102 to central connection spring 501. The sixmovable substructures 51 may be excited into a common oscillation mode.

The first four movable substructures 51 each have a trampoline-structureCoriolis element 90. Substructures 51 that are movable in thex-direction permit a differential detection of a yaw rate about they-axis. Substructures 51 that are movable in the y-direction permit adifferential detection of a yaw rate about the x-axis. The twoadditional substructures 51 that are diagonally movable in the x-y planeeach have a grid-structure Coriolis element 70 and permit a differentialdetection of a yaw rate about the z-axis.

1-19. (canceled)
 20. A yaw-rate sensor comprising: a substrate and aplurality of movable substructures that are mounted over a surface ofthe substrate, the movable substructures being coupled to a sharedspring element and the movable substructures having Coriolis elements;means for exciting the movable substructures into a coupled oscillationin a plane that extends parallel to the surface of the substrate; meansfor detecting deflections of the Coriolis elements caused by a Coriolisforce; a first Coriolis element for detecting a yaw rate about a firstaxis; and a second Coriolis element for detecting a yaw rate about asecond axis; wherein the second axis is not oriented parallel to thefirst axis.
 21. The yaw-rate sensor as recited in claim 20, eachCoriolis element being connected via additional spring elements to adrive frame of one of the substructures; the Coriolis elements beingconnected to the shared spring element.
 22. The yaw-rate sensor asrecited in claim 20, each Coriolis element being connected viaadditional spring elements to a drive frame of one of the substructures;and the drive frame of each substructure being connected to the sharedspring element.
 23. The yaw-rate sensor as recited in claim 20, a commoncenter of mass of at least two movable substructures remaining fixedduring one oscillatory period.
 24. The yaw-rate sensor as recited inclaim 20, at least one Coriolis element being connected via flexuralspring elements to a substructure; the flexural spring elementsexhibiting a high level of stiffness in the direction of the oscillationof the substructure; the flexural spring elements exhibiting a low levelof stiffness in a second direction which is oriented perpendicularly tothe direction of oscillation of the substructure and parallel to thesurface of the substrate; and means being provided for detecting adeflection of the Coriolis element in the second direction, caused by aCoriolis force.
 25. The yaw-rate sensor as recited in claim 20, at leastone Coriolis element being designed as a rocker; the Coriolis elementbeing connected via torsional spring elements to a substructure; thetorsional spring elements forming a rotary axis of motion of the rockerthat extends parallel to the surface of the substrate; the two sides ofthe rocker having different masses, in response to a Coriolis forceacting perpendicularly to the surface of the substrate, the Corioliselement being rotatable about the rotary axis of motion; and means beingprovided for detecting a rotation of the Coriolis element.
 26. Theyaw-rate sensor as recited in claim 20, at least one Coriolis elementbeing connected via flexural spring elements to a substructure; theflexural spring elements exhibiting a high level of stiffness indirections that extend parallel to the surface of the substrate; theflexural spring elements exhibiting a low level of stiffness in a seconddirection that extends perpendicularly to the surface of the substrate;and means being provided for detecting a deflection of the Corioliselement in the second direction, caused by a Coriolis force.
 27. Theyaw-rate sensor as recited in claim 20, at least one movablesubstructure having more than one Coriolis element.
 28. The yaw-ratesensor as recited in claim 20, further comprising means for exciting twomovable substructures into an oscillation mode that essentially inducesan antiphase deflection of the two movable substructures along a sharedaxis.
 29. The yaw-rate sensor as recited in claim 28, the two movablesubstructures, which are excitable into a common oscillation modeaccompanied by antiphase deflection, having one Coriolis element each;the two Coriolis elements being deflectable in opposite directions inresponse to a Coriolis force.
 30. The yaw-rate sensor as recited inclaim 20, four movable substructures being provided; means beingprovided for exciting the four movable substructures into a coupledoscillation mode; which essentially induces an antiphase deflection of afirst and of a second movable substructure along a first axis; and whichessentially induces an antiphase deflection of a third and of a fourthmovable substructure along a second axis.
 31. The yaw-rate sensor asrecited in claim 30, further comprising means for exciting anoscillation mode whereby the deflection of the first and second movablesubstructure proceeds in phase with the deflection of the third andfourth movable substructure.
 32. The yaw-rate sensor as recited in claim30, further comprising means for exciting an oscillation mode wherebythe deflection of the first and second movable substructure proceeds inphase opposition to the deflection of the third and fourth movablesubstructure.
 33. The yaw-rate sensor as recited in claim 30, theCoriolis elements being provided for determining yaw rates about threemutually perpendicularly extending axes.
 34. The yaw-rate sensor asrecited in claim 30, the first and the second movable substructurehaving a substantially identical first mass; the third and the fourthmovable substructure having a substantially identical second mass; thecentral spring element having a first spring stiffness in the directionof the first axis; the central spring element having a second springstiffness in the direction of the second axis; and the first mass, thesecond mass, the first spring stiffness and the second spring stiffnessbeing selected in such a way that the four movable substructures areexcitable into an oscillation mode having substantially the samedeflection amplitude for all four movable substructures.
 35. Theyaw-rate sensor as recited in claim 30, the third and the fourth movablesubstructure being mounted on the surface of the substrate in such a waythat a portion of the surface of the third and fourth movablesubstructure covers a region of the surface of the substrate thatresides between the first and the second movable substructure.
 36. Theyaw-rate sensor as recited in claim 20, the shared spring element beingcomposed of a plurality of tines and connecting elements; each tineincluding a first kink at a 90° counterclockwise position, a firststraight section of a first length, a second kink at a 90° clockwiseposition, a second straight section of a second length, a third kink ata 90° clockwise position, and a third section of a first length; eachconnecting element having a fourth kink at a 90° counterclockwiseposition and a fourth section of a third length; each tine beingfollowed by either a connecting element or another tine; a tinefollowing each connecting element; and the spring element forming aclosed ring.
 37. The yaw-rate sensor as recited in claim 20, the sharedspring element being designed as a ring, the movable substructures beingcoupled to the central spring element via connecting pieces that arejoined to the ring.
 38. The yaw-rate sensor as recited in claim 20,wherein the movable substructures are coupled to a shared, centralspring element and wherein the second axis is oriented perpendicular tothe first axis.
 39. A micromechanical ladder spring for suspendingCoriolis elements, comprising: two substantially parallel bars; the twobars being joined over the length thereof by a plurality of connectingrungs; and wherein interspacing between the plurality of connectingrungs is at least as great as the distance between the bars.